Always useful to either set a gank, or get away. This is a must!
I like to have it to boost my AP when im ganking. You can have anything you like for this skill. Its not a must, just get what you like most.
First get shadow walk at 1, just to scout ahead.
Then 1 in Hate Spike for minion farms.
Then just max Ravage ASAP for quick ganks. Then max shadow walk for a longer stealthtimer (Always useful). Put a point in Malice and Spite whenever you can. Hate Spike isnt that useful, so just max it last.
Well, I like to have the extra AP and Magic Pen. Just correct me if im wrong here, not entirely sure. Just use whatever runes fit you best
Dont bother getting HP. Its either a pubstomp for you, or you get raped. HP wont do any better since you wont be able to kill if you get HP. (This is just my opinion). As long as they dont buy oracles and wards youre safe, else play really defensive.
Start off with Dorans Ring + hp pot.
First time back: Boots of Speed (+Amplifying tome?)
Second time back: Mejais Soulstealer
Then just build Lich Bane ASAP (If you prefer, boots of mobility before). Zhonyas Ring as finisher